Electrodeposition of metals



T. w. s. HUTCHINS ELECTRODEPOS ITION OF METALS Filed Feb. 5. 1923 Patented F eb. 24, 1925.

UNITED STATEfi I C- E ELEGTRODEPOSITION 0F Application filed February 5, 1923. Serial No. 617,108.

T 0 all whom it may concern Be it known that I, THOMAS, IVILLIAM STAINER HUrcHrNs, a subject of the King of Great Britain and Ireland, and resident of Da-venh-am, in the county of Chester, England, have invented certain new and useful Improvements Relating. to the Electrodeposition of Metals,of' which the. following is a specification.

In the process of electrolytically depositing metals such as iron, nickel and cobalt, considerable difficulty, has been experienced owing to the deposited metal not being homogeneous but exhibiting various faults and being pitted with what are commonly termed hydrogen craters.

It is generally held that hydrogen bubbles result from the decomposition of the water content of the electrolyte and. attach themselves to the cathode as points upon i which metal is prevented from depositing and numerous attempts have been made to' obviate the difficulty either in the direction of preventing the decomposition of the water content of the electrolyte and therefore the formation of the hydrogen bubbles or in the direction of removing the hydrogen bubbles from the cathode as soon as they are formed, \o

By investigation and experiment, I have found that when solid particles (for instance of carbon) of a nature which would form a couple with the metal deposited are presout in the electrolyte, such particles or some of them :become attached to the deposited metal and at the point of contact a hydrogen crater or point is formed even though the electrolyte be neutral to methyl orange.

My invention comprises the provision of means which will ensure that the electrolyte round the cathode shall be completely freed from solid foreign matter in suspension of anature which would form a couple with the metal deposited.

My invention further comprises the provision of one or more recuperators containing portions of a similar metal (and/or basic compound or compounds of the same), to that being deposited through which the electrolyte is circulated from and 'to the electrolyzer, the said recuperators retaining the electrolyte out of contact with the atmosphere so that by the solution of the metal and/or basic compound or com-pounds of the same to replace at least in part, the metal deposited at the cathode, the electrolyte is rendered neutral.

In the application of my invention to the electrolytic deposition of iron, the electrolyzer is arranged in series with one or more recuperators containingscrap or other iron and exposing a considerable surface to the action ofthe electrolyte. The recuperators are sealed against the entry of air and the cross section of such recuperators in proportion to the flow of electrolyte is limited so as to ensure a sufficient scrubbing or washing action on the surface of the scrap metal in such recuperators as to cause the removal therefrom of the impurities in such metal which are insoluble in the electrolyte. The accumulation of such impurities upon the surface of the metal reduces the rate of recuperation of the electrolyte and increases the difficulty of maintaining the latter neutral. Further, the area of the electrolyte exposed to the atmosphere is limited in proportion to the area of scrap metal exposed to the electrolyte. The combination of these factors assures the dissolving of the metal bv the electrolyte sufficient to replace (either entirely from the scrap iron within the recuperators, or partly therefrom and partly from the anode) the metal deposited at the cathode and to neutralize the action of the atmosphere upon the portion of the electrolyte exposed thereto so restoring the electrolyte to a neutral condition which is of considerable importance in ensuring the deposition of a homogeneous mass.

The electrolyte passing from the recuperators into the electrolyzer is passed through one or more-filters which ensure that the liquid delivered therethrough is entirely free from solid matter in suspension of a nature which would form a couple with the metal deposited. If desired, more than one filter maybe used, one of which may extract thehea-vier matter or sludge in a manner similar to'that heretofore proposed in connection with electrolytic deposition processes. The final filter or the one which ensures the complete removal of the most 'minute particles mayx consist of felt, or earthenware, either alone or in conjunction with a centrifugal form of mechanical separator of the hydro-extractor type.

The anode itself is separated from the cathode by means of a diaphragm or filter to prevent any disintegrated solid matter of a natlire which would form a couple with the metal deposited passing from the anode into the electrolyte around the cathode. The anode may be made. of a metal which is insoluble in the electrolyte and a similar metal to that being deposited (which may be in the form of turnings, filings or like small grade parts) be packed between such anode and the filter or diaphragm. The use ofan insoluble anode in the manner described may considerably cheapen the process. l

The electrolyzer may be provided with a readily removable cover for convenience of access to the cathode and the latter may be rotated to ensure evenness of the deposit.

The rate of flow of electrolyte to the electrolyzer should preferably be such that the overflow from the latter (which passes to the recuperator or recuperators) shall be neutral to methyl orange. The solution I prefer to employ as electrolyte preferablyconsists of:,150 grammes ferrous sulphate FeSO (7 H 0), 100 grammes so-.

is therefore economical and simple and the 'i raw material thereof cheap. It is understood that whilst the description deals more especially with the deposition of iron, a similar process modified to suit the special conditions serves for the deposition of nickel and/or such other metals as contain amongst their impurities matters which are insoluble in the electro lyte and are of a nature which would form a couple with the metal being deposited.

Referring to the accompanying explanatory drawings which illustrate in diagram form, an electrolyzer plant for the deposition of iron, constructed and arranged in one convenient -form in accordance w1th my invention, Figure 1 being a general view of the plant and Figure 2 a cross section of.the electrolyzer, the deposition of the metal takes place in the vessel 4: in which is mounted a trough-like element 6 which constitutes the anode and a rotating cylindrical element a constituting the cathode. The latter in the illustration is disposed horizontally and rotated by a belt pulley d but it may be disposed vertically. Between the cathode and the anode is arranged a filter cloth 6 as shownin the detail view,

Figure 2 which prevents any disintegrated solid matter. or a nature which would form a couple with the metal being deposited from passing into the electrolyte around the cathode. i

The vessel a has a mid-feather f with an overflow aperture (not shown) therein which allows electrolyte to overflow into the compartment 9 whence it flows by the pipe h to the inlet of a pump 2'. Electrolyte may flow intothe compartment 9 along the shaft 7' which passes through the mid-feather i, no packing gland being provided around the shaft, but the amount of electrolyte so flowing will in practice be small.

The electrolyte is circulated by the pump 2' through the recuperators'"k Z m and the filter n back to the vessel a. Each of the recuperators is packed with the scrap or other iron and is made of considerable length relatively to its width. A baffle plate 0 is provided in each recuperator to prevent the mouth of the liquid pipe being covered by the scrap iron or other material in the recuperator. The vessel m is steam jacketed for heating purposes.

Each recuperator is sealed by a cover p against the entry of air and has a sludge cock 9 for the withdrawal of solid impurities which accumulate as the iron goes into solution.

'The filter 1?. may be of any suitable construction and arrangement and removes from, the electrolyte any solid matter of a nature which would form a couple with the metal being deposited, such as graphite, which may come over from the recuperators.

I claim 1. In an apparatus for the electro-deposition of metals, a vessel containing an elec-' trolyte, a cathode and an anode arranged in said vessel. means for circulating the elec trolyte, and filtering means arranged immediately adjacent the cathode and isolating the latter from the anode, the filtering means being adapted to completely free the electrolyte around the cathode from all foreign sol-id impurities of a nature which would become a couple withthe "metal being deposited.

2. An apparatus as claimed in claim 1 characterized by the provision of a relatively long narrow and air-tight vessel connected with the circulating means and con taining metal to be dissolved. said circulating" means being adapted to cause the electrolyte to pass through the last mentioned vessel with sufiicient velocity to exert a'scrubbing action on the metal whereby to remove any impurities in the metal being dissolved from the surface of the same.

3. Anapparatus as claimed in claim 1 characterized in thatv the area of the surface of the electrolyte incontact with the air is limited to the portion of' said electrolyte contained in the vessel whereby, with the assistance of the metal to be dissolved, the electrolyte is maintained in a neutral condition.

4. In an apparatus for electro-deposition of metals, a vessel containing an electrolyte,

vcharacterize a cathode and an anode arranged in said vessel, and a filtering diaphragm for filtering the electrolyte, said diaphragm constituting means isolating the cathode from the anode.

' 5. An ap aratus as claimed in claim 4 g by the provision of means for circulating the electrolyte, and filtering means arranged in the circulating means, the filtering means being adapted to completely free the electrolyte around the cathode from all foreign solid impurities of a nature which would form a couple with the metal being deposited.

6. An apparatus as claimed in claim 4, characterized by the provision of means for circulating the electrolyte. through and, externally of the vessel, relatively long narrow and air-tight vessels connected with the circulating means and containing metal to be dissolved, means for passing the electrolyte through the last mentioned vessels with suflicient velocity to exert a scraping action on the metal whereby to remove any impurities in the metal being dissolved from the surface of the same.

7. An apparatus as claimed in claim 4 characterized by the provision of means for circulating the electrolyte through and externally of the vessel, relatively long narrow and air-tightvessels connected with the circulating means and containin metal to be dissolved, means for passing t e electrolyte through the last mentioned vessels with sufiicient velocity to exert a scraping action on the metal whereby to remove any impurities in the metal being dissolved from the surface of the same, and filtering means arranged in the circulating means for filtering out the impurities.

8. An apparatus as claimed in claim 4 characterized by the provision of means for circulating the electrolyte, vessels connected with the circulating means and containingmetal to be dissolved, said circulating means acting to pass the electrolyte through the last mentioned vessels with sufiioient ve locity to exert a scraping action on the metal whereby to remove any impurities in the metal being dissolved from the surface of the same, and means rendering the last mentioned vessels air-tight whereby the area of the surface of the electrolyte in contact with the air is limited to the portion of said electrolyte contained in the vessel, and with the assistance of the metal to be dissolved, the electrolyte is maintained in a neutral condition. y

9. In an apparatus for electro-deposition of metals, a vessel containing an electrolyte, a cathode and an anode" arranged in said vessel filtering means arranged between the cathode and anode, said anode being insoluble in the electrolyte, and a metal similar to that being deposited packed between the anode and filtering means. i p

In testimony whereof I have signed my name to this specification.

THOMAS WILLIAM STAINER HUTCHINS. 

